June 23, 2025 • 10 mins
The problem with seaweed aquaculture is that it’s not always as ocean-friendly as it seems. While seaweed farming is often praised as a climate solution—able to sequester carbon, improve water quality, and support sustainable food systems—scientists are now warning that its rapid, unregulated expansion could be damaging vital marine ecosystems. In this episode of How to Protect the Ocean, we dive into how seaweed farms are being placed over seagrass meadows, disrupting fish nurseries, smothering biodiversity, and altering water chemistry in ways we’re only beginning to understand.
You’ll hear about the overlooked risks, from nutrient depletion and fertilizer runoff to coral reef shading and invasive species. We also explore solutions: better regulations, smarter zoning, and the importance of protecting seagrass habitats that store carbon and support marine life. Seaweed aquaculture can be part of the solution, but only if we act with caution and science in mind.
Link to article: https://theconversation.com/expanding-seaweed-farms-pose-a-risk-to-vital-marine-life-248329
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
seaweed farms are sprouting up all over the world, offering potential climate, food, andcoastal benefits.
But a recent warning from scientists says grow too much too fast and we couldinadvertently be harming critical marine habitats like seagrass.
Today we explore on this how to protect the ocean podcast how this green wave might have adark side.
(00:21):
Let's start the show.
Hey everybody, welcome back to another exciting episode of the How to Protect the Oceanpodcast.
I'm your host, Andrew Lewin, and this is the podcast where you find out what's happeningwith the ocean, how you could speak up for the ocean, and what you can do to live for a
better ocean by taking action.
On today's episode, we're going to be talking about seaweed farming and how it could benegatively affecting seagrass habitats.
(00:44):
And the one thing that I was talking to a bunch of buddies of mine, colleagues, buddies,they're really good friends of mine, are the Project Seagrass people.
They were at UNOC, the United Nations Ocean Conference in Nice, France a couple of weeksago.
And we talked a lot about
How seagrass takes a backseat to coral reefs and without seagrasses you don't really havehealthy coral reefs and vice versa without healthy coral reefs you don't really have
(01:09):
healthy seagrasses they depend on each other same with mangroves all those can be a reallygood system if everything is healthy and they can secure the coastline offer a lot of
biodiversity benefits to each and every one of those habitats because they all play a rolebut if they're mismanaged
then those health benefits and all those biodiversity benefits go downhill and the entiresystem can be at risk global seaweed agriculture comes into play here as is being pushed
(01:36):
because it's been valued at seventeen billion dollars u s in twenty twenty three projectedto double by twenty thirty two largely driven by the demand in asia to see we can help
with carbon capture
fertilizers, food, even renewable plastics, but if it's mismanaged, it threatens vitalhabitats and biodiversity, just like we talked about for seagrasses.
(01:58):
Here's the thing, when you have a seaweed farm,
to generate money and offer all these benefits I just talked about.
You often put it on top of a seagrass meadow, a seagrass bed, just because it offers thatextra health aspect.
So usually what was happening is when seaweed farms didn't have seagrass beds underneath,there was a lot of diseases which harmed the actual seaweed and its ability to create all
(02:23):
these wonderful things.
Scientists started to say, hey, you know what, let's put the seaweed on top of seagrassbeds and then the seaweed becomes better.
becomes healthier and it becomes easier to work with.
The problem is now that seaweed is becoming a huge thing in the market.
we're going to see a threat to seagrass beds, which is already starting to see threats.
(02:44):
We've had the people from Project Seagrass a number of times on the podcast.
Major threats like anchoring boats in seagrass meadows.
People don't think seagrasses are a big deal.
They're a huge deal.
Like I said before, they have a lot of animals that rely on seagrass beds to hide frompredators.
They rely for food, whether it's the seagrasses themselves or the animals that hide withinthere.
(03:04):
It's a plentiful area and a benefit to a lot of animals.
And when you start to scrape
anchors or you start to
move them around or take them out because people don't want to have sea grasses in theirfeet when they go in on the beach if they're near a resort or if they're near a popular
beach you start to take away the benefits of those sea grasses so we're already seeing alot of pressure on sea grasses and Project Sea Grass and their partners and their networks
(03:30):
are trying to restore sea grasses which is very difficult to do it's not an easy thing todo hasn't been done a lot before there are a lot of projects out there some are successful
and some aren't depending on the type of species that they're
depending on the environment that they're working in.
There's a lot of problems when it comes down to it.
And so we need to ensure that seagrass beds and habitats are protected.
(03:54):
The ones that are already there are protected.
Having this boom of seaweed poses a risk to these seagrass beds because we are seeing likeless protection for these seagrass beds.
And if you start to push them all in certain areas like Asia and other places, you'llstart to see a reduction in the habitat of seagrasses, which is a bad thing.
(04:16):
You know, something that could be detrimental to not only seagrass beds in general, butalso biodiversity around the ocean and around the
world as well as just you know protection for other habitats and health of other habitatsand protection of shoreline.
So this loss of seagrass meadows because of seaweed farms is not great.
(04:37):
and especially in Southeast Asia.
these metals, you know, they support fish nurseries, oxygen production, sedimentstabilization, and farming infrastructure can smother and damage the seagrass habitat.
So it's not always great.
Other risks are nutrient imbalance and pollution.
Rapid growth may deplete nutrients.
When that happens, artificial fertilizers may be used, raising neutrophilication, algalblooms, oxygen depletion, and so forth.
(05:04):
of course is also invasive species in genetic spread so farms can introduce non-nativespecies or varieties and diseases escape spores may alter local dynamics if you take
seaweed from one place and you start to grow it in another place with oftentimesaquaculture does like liquid it does for the atlantic salmon it'll take atlantic salmon
from the atlantic and it'll grow it in the pacific as it provides
(05:25):
better habitat for that and a better area for that.
So imagine doing that with seaweed, your spores of seaweed that gets into a new habitat ora new environment that becomes invasive that can take over the area and it can cause more
damage to the area, including seagrass beds.
And of course you have coral competition.
in tropical seas, dense seaweeds can directly harm corals through shading, chemicalwarfare and space competition.
(05:49):
So seaweed can be harmful to a lot of places.
So having this widespread push
for seaweed farming needs to slow down there needs to be precautions that are taken inthis is what we do as humans as a population we start to look at one solution like all
this is a great solution let's push it to the maximum and less ramp it up and let's do itas much as we can and then we do it we start to realize that there's some damages that can
(06:15):
happen let's not look at the ethics before happens and
when we look back at it, need to say, look, these are the ethics that we need to thinkabout.
We need to go through it as a precautionary approach.
Just like we're talking about when Dr.
Andrew Thaler was on the podcast talking about the opportunities that we have with deepsea mining.
This deep sea mining will probably go through in some cases and in some places, but wehave an opportunity to do what's right.
(06:37):
We have an opportunity to regulate the heck out of it, making sure that we are protectingthe environment while doing it and going slowly and making sure that we are doing what is
right.
Same thing with seaweed farming.
We need to proceed with caution.
Do study pilots.
Make sure they go on for years and make sure we are looking at how this affects seagrasshabitats as well as a seaweed as a product and making sure that we're protecting it.
(07:01):
Also, just looking at, hey, you know what?
Maybe we shouldn't put seaweed farms everywhere we see seagrasses because seagrasses areimportant and we know that the seaweed farms can actually harm the seagrass beds.
It's hard to say both of these.
So that could be a big problem.
These are something that we have to see.
So some real world examples are having Southeast Asia and the Western Indian Ocean.
(07:22):
Some farms have outright replaced seagrass habitats, which is not good.
And in the UK, murrel beds, ancient red algae formations, are being smothered by fastgrowing farm species fostered by nutrient runoff.
So obviously not a good thing.
Now the upside is, seaweed does help remove nutrients from coastal waters, use andintegrate it in multi-trophic systems.
(07:43):
to treat ocean to you trophic water so there are some benefits to it as some farmers haveturned sargassum overgrowth into simple products such as fertilizer you know building
materials and even feedstocks so there are some benefits that's key here is it proceedwith caution this is something that we say with everything just like i said when we bring
things up too quickly
(08:04):
things get out of hand.
So the expert takeaways and guidelines scientists argue that we need zoning to avoidsensitive habitats and nutrient budgeting before scaling up the farms.
Proceed with caution, just like I said.
Regulations should restrict non-native strains and mandate monitoring and adaptivemanagement, and then learn from shellfish aquaculture, riparian buffer zones, and
(08:26):
integrated systems to design low-impact seaweed farms.
There are ways to go about this the right way.
pushing this and ramping up too fast where there's no guidelines or the guidelines aren'tbeing followed can really damage seagrass beds for the long term.
And that's not what we need.
There are not enough seagrass beds around.
There's not enough money put into the restoration and protection of seagrass beds.
(08:48):
They are a habitat that is vulnerable to not only extinction and extirpation in certainareas, but degradation and just bad health is really what it comes down to.
So, seaweed farming is not the silver bullet, but when guided by smart science andregulation, it can be powerful too.
I highly recommend that they team up with seagrass scientists and making sure that thingsare done science-based and the decision-making is science-based and the management is
(09:16):
science-based.
Do get the theme here?
Science-based rules.
This is what we need to do when we go forward with seaweed farms.
We're not saying that seaweed farms are bad.
But when you start to put seaweed farms over seagrass beds every single time, and thatstarts to be widespread and scales up, that could be detrimental to seagrass beds,
detrimental to biodiversity, detrimental to shoreline security, and detrimental to theocean in general.
(09:39):
Let's ensure we harvest solutions without uprooting the foundations of marine life.
That's really what it comes down to.
I'm gonna stop it there.
I'd love to hear your thoughts.
Do you think that seaweed farms should be scaling up?
without any of these guidelines or how do you think these guidelines should beimplemented?
Should they be mandatory in different regions of the world?
(10:00):
Love to hear your thoughts.
You can hit me up in the comments below.
If you're listening to the audio podcast, you can hit me up on the websites, go tospeakupforblue.com forward slash contact, fill out the form.
It goes right to my email or you can DM me on Instagram at how to protect the ocean.
And if you want more ways to guide you to better ocean action, join the undertow, go tospeakupforblue.com forward slash join the undertow.
(10:22):
That's speak up for blue.com forward slash join the undertow.
I want to thank Dr.
Benjamin Jones and Dr.
Richard Unsworth for writing this article in the conversation.
I'm to link to that below and I want to thank you for joining me on today's episode of thehow to protect the ocean podcast.
I'm your host, Andrew Lewin from the true north strong and free.
Have a great day.
We'll talk to you next time and happy conservation.
seaweed farms are sprouting up all over the world, offering potential climate, food, andcoastal benefits.
But a recent warning from scientists says grow too much too fast and we couldinadvertently be harming critical marine habitats like seagrass.
Today we explore on this how to protect the ocean podcast how this green wave might have adark side.
(00:21):
Let's start the show.
Hey everybody, welcome back to another exciting episode of the How to Protect the Oceanpodcast.
I'm your host, Andrew Lewin, and this is the podcast where you find out what's happeningwith the ocean, how you could speak up for the ocean, and what you can do to live for a
better ocean by taking action.
On today's episode, we're going to be talking about seaweed farming and how it could benegatively affecting seagrass habitats.
(00:44):
And the one thing that I was talking to a bunch of buddies of mine, colleagues, buddies,they're really good friends of mine, are the Project Seagrass people.
They were at UNOC, the United Nations Ocean Conference in Nice, France a couple of weeksago.
And we talked a lot about
How seagrass takes a backseat to coral reefs and without seagrasses you don't really havehealthy coral reefs and vice versa without healthy coral reefs you don't really have
(01:09):
healthy seagrasses they depend on each other same with mangroves all those can be a reallygood system if everything is healthy and they can secure the coastline offer a lot of
biodiversity benefits to each and every one of those habitats because they all play a rolebut if they're mismanaged
then those health benefits and all those biodiversity benefits go downhill and the entiresystem can be at risk global seaweed agriculture comes into play here as is being pushed
(01:36):
because it's been valued at seventeen billion dollars u s in twenty twenty three projectedto double by twenty thirty two largely driven by the demand in asia to see we can help
with carbon capture
fertilizers, food, even renewable plastics, but if it's mismanaged, it threatens vitalhabitats and biodiversity, just like we talked about for seagrasses.
(01:58):
Here's the thing, when you have a seaweed farm,
to generate money and offer all these benefits I just talked about.
You often put it on top of a seagrass meadow, a seagrass bed, just because it offers thatextra health aspect.
So usually what was happening is when seaweed farms didn't have seagrass beds underneath,there was a lot of diseases which harmed the actual seaweed and its ability to create all
(02:23):
these wonderful things.
Scientists started to say, hey, you know what, let's put the seaweed on top of seagrassbeds and then the seaweed becomes better.
becomes healthier and it becomes easier to work with.
The problem is now that seaweed is becoming a huge thing in the market.
we're going to see a threat to seagrass beds, which is already starting to see threats.
(02:44):
We've had the people from Project Seagrass a number of times on the podcast.
Major threats like anchoring boats in seagrass meadows.
People don't think seagrasses are a big deal.
They're a huge deal.
Like I said before, they have a lot of animals that rely on seagrass beds to hide frompredators.
They rely for food, whether it's the seagrasses themselves or the animals that hide withinthere.
(03:04):
It's a plentiful area and a benefit to a lot of animals.
And when you start to scrape
anchors or you start to
move them around or take them out because people don't want to have sea grasses in theirfeet when they go in on the beach if they're near a resort or if they're near a popular
beach you start to take away the benefits of those sea grasses so we're already seeing alot of pressure on sea grasses and Project Sea Grass and their partners and their networks
(03:30):
are trying to restore sea grasses which is very difficult to do it's not an easy thing todo hasn't been done a lot before there are a lot of projects out there some are successful
and some aren't depending on the type of species that they're
depending on the environment that they're working in.
There's a lot of problems when it comes down to it.
And so we need to ensure that seagrass beds and habitats are protected.
(03:54):
The ones that are already there are protected.
Having this boom of seaweed poses a risk to these seagrass beds because we are seeing likeless protection for these seagrass beds.
And if you start to push them all in certain areas like Asia and other places, you'llstart to see a reduction in the habitat of seagrasses, which is a bad thing.
(04:16):
You know, something that could be detrimental to not only seagrass beds in general, butalso biodiversity around the ocean and around the
world as well as just you know protection for other habitats and health of other habitatsand protection of shoreline.
So this loss of seagrass meadows because of seaweed farms is not great.
(04:37):
and especially in Southeast Asia.
these metals, you know, they support fish nurseries, oxygen production, sedimentstabilization, and farming infrastructure can smother and damage the seagrass habitat.
So it's not always great.
Other risks are nutrient imbalance and pollution.
Rapid growth may deplete nutrients.
When that happens, artificial fertilizers may be used, raising neutrophilication, algalblooms, oxygen depletion, and so forth.
(05:04):
of course is also invasive species in genetic spread so farms can introduce non-nativespecies or varieties and diseases escape spores may alter local dynamics if you take
seaweed from one place and you start to grow it in another place with oftentimesaquaculture does like liquid it does for the atlantic salmon it'll take atlantic salmon
from the atlantic and it'll grow it in the pacific as it provides
(05:25):
better habitat for that and a better area for that.
So imagine doing that with seaweed, your spores of seaweed that gets into a new habitat ora new environment that becomes invasive that can take over the area and it can cause more
damage to the area, including seagrass beds.
And of course you have coral competition.
in tropical seas, dense seaweeds can directly harm corals through shading, chemicalwarfare and space competition.
(05:49):
So seaweed can be harmful to a lot of places.
So having this widespread push
for seaweed farming needs to slow down there needs to be precautions that are taken inthis is what we do as humans as a population we start to look at one solution like all
this is a great solution let's push it to the maximum and less ramp it up and let's do itas much as we can and then we do it we start to realize that there's some damages that can
(06:15):
happen let's not look at the ethics before happens and
when we look back at it, need to say, look, these are the ethics that we need to thinkabout.
We need to go through it as a precautionary approach.
Just like we're talking about when Dr.
Andrew Thaler was on the podcast talking about the opportunities that we have with deepsea mining.
This deep sea mining will probably go through in some cases and in some places, but wehave an opportunity to do what's right.
(06:37):
We have an opportunity to regulate the heck out of it, making sure that we are protectingthe environment while doing it and going slowly and making sure that we are doing what is
right.
Same thing with seaweed farming.
We need to proceed with caution.
Do study pilots.
Make sure they go on for years and make sure we are looking at how this affects seagrasshabitats as well as a seaweed as a product and making sure that we're protecting it.
(07:01):
Also, just looking at, hey, you know what?
Maybe we shouldn't put seaweed farms everywhere we see seagrasses because seagrasses areimportant and we know that the seaweed farms can actually harm the seagrass beds.
It's hard to say both of these.
So that could be a big problem.
These are something that we have to see.
So some real world examples are having Southeast Asia and the Western Indian Ocean.
(07:22):
Some farms have outright replaced seagrass habitats, which is not good.
And in the UK, murrel beds, ancient red algae formations, are being smothered by fastgrowing farm species fostered by nutrient runoff.
So obviously not a good thing.
Now the upside is, seaweed does help remove nutrients from coastal waters, use andintegrate it in multi-trophic systems.
(07:43):
to treat ocean to you trophic water so there are some benefits to it as some farmers haveturned sargassum overgrowth into simple products such as fertilizer you know building
materials and even feedstocks so there are some benefits that's key here is it proceedwith caution this is something that we say with everything just like i said when we bring
things up too quickly
(08:04):
things get out of hand.
So the expert takeaways and guidelines scientists argue that we need zoning to avoidsensitive habitats and nutrient budgeting before scaling up the farms.
Proceed with caution, just like I said.
Regulations should restrict non-native strains and mandate monitoring and adaptivemanagement, and then learn from shellfish aquaculture, riparian buffer zones, and
(08:26):
integrated systems to design low-impact seaweed farms.
There are ways to go about this the right way.
pushing this and ramping up too fast where there's no guidelines or the guidelines aren'tbeing followed can really damage seagrass beds for the long term.
And that's not what we need.
There are not enough seagrass beds around.
There's not enough money put into the restoration and protection of seagrass beds.
(08:48):
They are a habitat that is vulnerable to not only extinction and extirpation in certainareas, but degradation and just bad health is really what it comes down to.
So, seaweed farming is not the silver bullet, but when guided by smart science andregulation, it can be powerful too.
I highly recommend that they team up with seagrass scientists and making sure that thingsare done science-based and the decision-making is science-based and the management is
(09:16):
science-based.
Do get the theme here?
Science-based rules.
This is what we need to do when we go forward with seaweed farms.
We're not saying that seaweed farms are bad.
But when you start to put seaweed farms over seagrass beds every single time, and thatstarts to be widespread and scales up, that could be detrimental to seagrass beds,
detrimental to biodiversity, detrimental to shoreline security, and detrimental to theocean in general.
(09:39):
Let's ensure we harvest solutions without uprooting the foundations of marine life.
That's really what it comes down to.
I'm gonna stop it there.
I'd love to hear your thoughts.
Do you think that seaweed farms should be scaling up?
without any of these guidelines or how do you think these guidelines should beimplemented?
Should they be mandatory in different regions of the world?
(10:00):
Love to hear your thoughts.
You can hit me up in the comments below.
If you're listening to the audio podcast, you can hit me up on the websites, go tospeakupforblue.com forward slash contact, fill out the form.
It goes right to my email or you can DM me on Instagram at how to protect the ocean.
And if you want more ways to guide you to better ocean action, join the undertow, go tospeakupforblue.com forward slash join the undertow.
(10:22):
That's speak up for blue.com forward slash join the undertow.
I want to thank Dr.
Benjamin Jones and Dr.
Richard Unsworth for writing this article in the conversation.
I'm to link to that below and I want to thank you for joining me on today's episode of thehow to protect the ocean podcast.
I'm your host, Andrew Lewin from the true north strong and free.
Have a great day.
We'll talk to you next time and happy conservation.
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